Magnetic plug for core bits



Febi17, 1953 o. HERNDON 2,628,322

MAGNETIC PLUG FOR CORE BITS Filed NOV. 18, 1949 3:"; -3 -1 -/5 M v/ Q /7 25 /a 6 T INVENTOR LAWRENCE o. HEBNDO/V,

%)7/mau;dum r ATTORNEYS Patented Feb. 17, 1953 2,628,822 MAGNETIC PLUG FOR CORE BITS I Lawrence 0. Herndon, Elk Basin, Wyo., assignor to J. E. Jones, Cody, Wyo.

Application November 18, 1949, Serial No. 128,066

This invention relates to protective magnetic plugs for core bits and more particularly to a magnetic plug to be carried in a diamond core bit to protect the bit from damage by metallic particles or fragments,

It is among the objects of the invention to provide a protective magnetic plug for a core bit which plug is freely slidable in the core bit so that it protrudes slightly at the bottom end of the bit when the bit is empty and is moved upwardly in the bit as a core enters the bit, which is provided with latch means engageable with the interior of the bit to prevent accidental loss of the plug from the bit, which includes strong permanent magnets and a housing of non-magnetic material supporting the permanent magnets and slidable in the bit, and which is simple and durable in construction, and easy to install in an existing core drill bit with no modification of the bit construction.

Other objects and advantages will become apparent from a consideration of the following description and the appended claims in conjunction with the accompanying drawing, wherein: Figure 1 is a longitudinal medial cross sectional view of a core drill bit showing a protective magnetic plug illustrative of the invention operatively mounted in the bit;

Figure 2 is a top plan view of the magnetic plug;

Figure 3 is a longitudinal cross section on the line 3-3 of Figure 2; and

Figure 4 is a bottom plan view of the protective plug.

With continued reference to the drawing, the core bit, generally indicated at I0, comprises an outer cylindrical shell or tube attachable at its upper end to a drill tube section, not illustrated, and having at its lower end an externally screw threaded portion |2 of reduced diameter and having its inner surface inclined inwardly toward the lower end of the shell. An annular diamond carrying nut or shoe I3 is threaded onto the portion |2 and extends over the end of this portion at the bottom end of the shell A cylindrical core sleeve M is secured in the shell I in circ-umspacial relationship to the latter and.

has its lower end spaced from the bottom end of the shell H and including an externally screw threaded portion I5, the threads of which terminate at an annular shoulder formation IS. A resilient finger formation I! is threaded onto the screw threaded portion l5 of the core receiving sleeve l4 and projects below the bottom end of the sleeve l4 and a resilient core retainer |8 is 5 Claims. (c1.255 '12).

. 2 mounted in the lower end of the formation ll to frictionally engage a core out by the bit and retain the core in the receiving sleeve M, the core retaining ring l8 being spaced from the adjacent end of the sleeve M, as is clearly illustrated in Figure 1.

As the core bit I0 is of well known construction, a more detailed description thereof is considered unnecessary for the purposes of the present disclosure.

The protective magnetic core of the present invention is generally indicated at 20 and comprises an elongated, cylindrical plug 2| of non-magnetic material, such as brass or bronze, divided into two portions by an annular shoulder 22 which extends around the plug body 2| adjacent the mid-length location of the body. The portion of the plug body above the shoulder 22 has a diameter slightly less than the internal diameter of the sleeve It so that the plug is freely slidable in the sleeve and the portion of the plug below the shoulder 22 has a diameter less than the diameter of the portion above the shoulder by the width of the shoulder. When the'plug is operatively mounted in the core bit, as illustrated in Figure 1, the shoulder 22 engages the upper end of the core retaining ring |8 when the bit is empty to restrain the plug 20 from falling out of the bit. As a core is cut by the bit and moves inwardly of the bit the plug is forced upwardly sliding in the sleeve M,

The plug body 2| is provided in its surface with a plurality of longitudinally extending, angularly spaced apart grooves 23 of arcuate cross sectional shape which grooves provide fluid passages so that drilling fluid can flow between the plug and the sleeve It. The plug is provided in its upper portion near the shoulder 22 with two diametrically opposed recesses 24 which are elon gated longitudinally of the plug and dogs 25 are respectively mounted in these recesses and urged outwardly of the recesses by springs 26 so that the outwardly turned lower ends of these dogs will enter the space between the bottom end of the sleeve l4 and the upper end of the core retaining ring l8 and provide an additional safety lock to prevent accidental loss of the plug from the drill.

The lower portion of the plug body 2| is provided with a coaxial, cylindrical bore or recess 21 which, in the arrangement illustrated, opens to the lower end of the plug body and terminates inwardly of the plug body adjacent the location of the shoulder 22. It is to be understood that the length of the plug body 2| is such as'to give the desired stability to the plug relative to the sleeve 14 of the bit and thatthe length of the 3 recess 21 may be greater or less in relationship to the length of the plug body than that illustrated in Figure 3 without in any way exceeding the scope of the invention.

The recess 21 has a diameter which is less than the outside diameter of the lower portion of the plug body by an amount sufficient only to leave a wall of sufficient thickness surrounding the recess to provide adequate strength for this lower portion of the plug body and a group of permanent bar magnets, as indicated at 28, 29, 3D and 3| are mounted in the recess 21 and protrude a slight" amount out of the open end of the recess. These permanent magnets extend longitudinally of the recess and are secured therein by suitable means such as the pin 32 of non-magnetic material'extending through diametrically opposite apertures in the plug body wall surrounding the recess and through registering apertures in the several-mag net bars. The adjacent magnets are spaced apart and separated by plates 32, 33 and 34 of nonmagnetic material which plates; are also-apertured, to receive the pin132,

The outer magnets 28 and 35' are of arcuate cross sectional shape so, that they fit: closely against the surface of the cylindrical: recess 2'! at diametrically opposite, sides of the recess and the inner magnets 29 and 30 are-bf, substantially rectangularcross-sectionalshape but have arcuately curved longitudinal edges which also fit theinternal curvature of the'recess 2 1 Before the bit in is reinserted intoa drill hole to continue drilling, the-magnetic-protective plug 29 is slipped into-the bottom, open end-of the drill and is held inthe drill in'the position illustrated in Figure-l by contactof the shoulder 22 with the upper end ofthe core retaining ring Hi. When the drill reaches the bottom of the drill hole the ends of the permanent-magnets pro-truding from the bottomend of theplug body 2i and somewhat below the nut or shoeit of thetdrill will attract to themselves any. metallic particles or'fragments onthe bottom-of the drill hole, removing such: fragmentsfrom the path of the diamond equipped shoeor nut l3to protecttthe drill from damage; by such metallic fragments or particles. As,the'plug'is-movedupwardly of the drillby the entry of: the core into, the drill-the metallic fragments or particles are carried along with the plug; and, when the drill is removed from thedrill hole-,the plug 20 is removed, cleaned and replaced before the drill is again lowered into the drill hole.

The invention may be embodied. in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is, therefore, to be considered ,in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, rather than by the foregoing description, and all changes which comewithin the meaning and range of equivalency of the claims are, therefore, intended to be embraced therein.

What is claimed is:

1; In combination with a core bit including an outershell attachable at its normally upper end to the normally lower end ofdrill tubesection and having a portion of its inner surface at its lower'end inwardly inclined, anannular. shoe threaded onto the shell at the lower endof the latter, a core sleeve disposed within saidshell and circumferentially spaced-therefrom; a spring finger formation threaded onto-said shelllat the end of thelatteradiacent-saidshoeand enga e:

able at its end remote from said sleeve with the inwardly inclined inner surface portion of said shell, and an annular core retainer supported by said spring finger formation coaxially of said sleeve and adjacent to but spaced from the end of said sleeve adjacent said shoe, a magnetic core bit plug comprising a plug body of non-magnetic material and of elongated cylindrical shape slidably received in said core sleeve. and having a longitudinally extending recess opening to the end thereof adjacent said shoe, means on said plug body engaging said core retainer and supporting said plug body in a position in which it extends through said core retainer with its end to which said reces opens at the end of said core retainer remote from said sleeve, and a group of permanent magnets disposed in the recess in said plug body and extending from the end of the latter to which said recess opens, said magnets extending through said shoe in the absence of a core in-saidbit and said plug being-slidable along said core sleeve away from said shoe by a core moving through said shoe. into said core sleeve.

2. In combination with acorebitincluding an outer shell attachable at its normally upper end to the normally lower end of a drill tube section and, having a portion of its inner surface at its lower end inwardly inclined, an annular shoe threaded onto the shell at the-lower end of the latter, a core sleeve disposed within said shell and-circumferentially spaced therefrom, a spring finger formation threaded onto said shell at the end of the latter adjacent saidshoe andengageableat its end remote from said sleeve with the inwardly inclined inner surface portion'of said shell, and an annular core retainer supported by said spring finger formation coaxially of said sleeve and djacent to but spaced from the end of said sleeve adjacent said shoe, a magnetic core bit plug comprising a plug body of non-magnetic material and of elongated cylindrical shape slidably received in said coresleeve and having a longitudinally extending recess opening. to the end thereof adjacent saidshoe, means on said plug body engaging said core retainer and supporting said plug body in a-position in which it extends through said core retainer with its end to which said recess opens at the end of said core retainer remote from said sleeve, and a group of permanent magnets disposed in the recess in said plug body and extending from the end of the latter to which said recess opens, said magnets extending through said shoe in the absence of a core in said bit and said plug being slidable along said core sleeve away from said shoe by a core moving through said shoe into said core sleeve, said plug body havingilongitudinally extending and angularly spaced apart grooves therein for the passage of fluid through said core sleeve past said plug.

3 Incombination with a core bit including an outer shell attachable at its normally-upper end to the normally lower end of .a drill tube section and having a portion of its inner surface .atits lower: end inwardly inclined, an annular shoe threaded onto the shell at the lower end of the latter, a core sleeve disposed within said shell and circumferentially spaced therefrom, a spring finger formation threaded onto said shell at the end of the latter adjacent said shoe andlengageable at its end remote from said sleeve with the inwardly inclined inner surface portionbf said shell, and an annular core retainer supported by said spring finger formation coaxially of said sleeveiand adjacent to but spaced fromthe end permanent magnets disposed iii-the recess in said plug .body and extending from the end of the latter to which said recess opens, said magnets extending through said shoe in the absence of a core in said bit and said plug being slidable along said core sleeve away from said shoe by a core moving through said shoe into'said core sleeve, said plug body having angularlyjspaced apart recesses therein, and dogs pivotally mounted one in each of said recesses and'spring urged into engagement in the space between the adjacent ends of said core sleeve and said core retainer to releasably secure said core bit lug at the end of said core sleeve adjacent said shoe.

4. In combination with a core bit including a core sleeve, an annular core retainer disposed adjacent one end of said core sleeve, and a resilient finger formation threaded onto said core sleeve at said one end of the latter and supporting said core retainer in position adjacent to but spaced from said one end of said core sleeve, a magnetic core plug comprising a plug body of non-magnetic material and of elongated cylindrical shape slidably received in said core sleeve and extending through said core retainer in the absence or a core in the latter, said body having a coaxial recess therein opening to the end thereof remote from said core sleeve, means on said body engaging said core retainer and precluding movement of said body out of said core sleeve through said core retainer, a group of permanent magnet bars disposed in side by side relationship in the recess in said plug body and projecting from the end of the latter to which said recess opens, separator plates of non-magnetic material disposed one between each two adjacent magnetic bars,

and meanssecuring said magnet bars and said separator plates in the recess in said plug body.

5. In combination with a core bit including a core sleeve, an annular core retainer disposed adjacent one end of said core sleeve, and a resilient finger formation threaded onto said core sleeve at said one end of the latter and supporting said core retainer in position adjacent to but spaced from said one end of said core sleeve, a magnetic core plug comprising a plug body of non-magnetic material and of elongated cylindrical shape slidably received in said core sleeve and extending through said core retainer in the absence of a core in the latter, said body having a coaxial recess therein opening to the end thereof remote from said core sleeve, means on said body engaging said core retainer and precluding movement of said body out of said core sleeve through said core retainer, a group of permanent magnet bars disposed in side by side relationship in the recess in said plug body and projecting from the end of the latter to which said recess opens, separator plates of non-magnetic material disposed one between each two adjacent magnet bars, means securing said magnet bars and said separator plates in the recess in said plug body, and means carried by said plug body and engaging said core sleeve at said one end of the latter releasably securing said plug in position in which it extends through said core retainer.

LAWRENCE O. HERNDON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 344,849 Miller et al. July 6, 1886 1,803,731 Scott May 5, 1931 1,806,001 Simms et al May 19, 1931 1,954,777 Garfield Apr. 10, 1934 2,092,316 Lane Sept. 7, 1937 2,177,300 Kellegrew Oct. 24, 1939 2,200,505 Kerr May 14, 1940 2,297,044 Barker et al. Sept. 29, 1942 

